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Biomedical subjects

J D Pearson

Publications and source records attributed to J D Pearson.

At least 145 records · Page 8Linked to original sources
PubMed1990

Modernization and catecholamine excretion of young Samoan adults.

Urinary catecholamine excretion rates have been used as a cross-culturally valid measure of generalized stress. The purposes of this paper are to examine group differences in catecholamine excretion rates in three Samoan groups who differ in degree of modernization and to compare these findings to rates of norepinephrine and epinephrine excretion in other populations. In 1986-1987, 24-hr urine samples were collected from 18-37-year-old Samoans; 46 rural Western Samoan villagers, 53 American Samoans, and 49 Samoans residing in Honolulu. The results show that norepinephrine excretion is significantly higher in more modernized Samoan groups (P less than 0.05), while epinephrine excretion is not significantly different in the three groups. The higher norepinephrine excretion rate in the more modernized Samoan groups may be related to differences in relative work load associated with changes in body weight, work capacity, and work patterns which accompany modernization. Samoan epinephrine excretion rates are relatively high compared to the results of other population studies, while norepinephrine excretion in three Samoan samples ranged from among the lowest rates observed worldwide to among the highest.

Adult↗
PubMed1990

Action of calcitonin gene-related peptide upon bovine vascular endothelial and smooth muscle cells grown in isolation and co-culture.

1. Bovine aortic endothelial cells (BAE) and smooth muscle cells (BASM) were grown separately and in co-culture. 2. Calcitonin gene-related peptide (CGRP) caused dose-dependent activation of adenylate cyclase in each cell type when grown in isolation. The concentration of CGRP causing half-maximal activation in BAE and BASM was 200 nM and 310 nM, respectively. 3. In cells grown in co-culture exposure to bradykinin produced dose-dependent elevations in cyclic GMP content which were maximal 1 min after application of the agonist. 4. CGRP (1 nM-1 microM) did not stimulate a rise in cyclic GMP in co-cultures. 5. Displaceable CGRP binding was identified throughout the wall of the bovine aorta. 6. We conclude that CGRP receptors coupled to adenylate cyclase are present on BAE and BASM, but there is no coupling of these receptors to the release of any agent (such as endothelium-derived relaxing factor) that activates guanylate cyclase.

Adenylyl Cyclases↗
PubMed1989

The hydrolysis of extracellular adenine nucleotides by arterial smooth muscle cells. Regulation of adenosine production at the cell surface.

The extracellular reaction sequence ATP----ADP----AMP----adenosine participates in regulating the time course of cellular response during crisis or signaling events, such as thrombus formation or neurotransmission. We have investigated the whole time course of hydrolysis of ATP to adenosine by recirculating adenine nucleotide substrates over smooth muscle cells attached to polystyrene beads. Kinetic parameters were estimated for each reaction by fitting observed time courses to models of the pathway. In spite of the inhibition of 5'-nucleotidase by ADP, adenosine was produced very rapidly by smooth muscle cells. Comparisons of the apparent Km values of ADPase and 5'-nucleotidase (determined from experiments in which each substrate was used as the initial substrate with Km values observed when each substrate was supplied from the upstream reaction) suggest that the local concentrations of substrate supplied from the preceding reactions are very much higher than those in the bulk phase. This enhancement of efficiency overcomes the effect of the feed-forward inhibition to give rise to very rapid adenosine production from ADP or ATP. These observations are in marked contrast to our previous findings with endothelial cells (Gordon, E. L., Pearson, J. D., and Slakey, L. L. (1986) J. Biol. Chem. 261, 15496-15504), on which feed-forward inhibition causes a profound lag in adenosine production from adenine nucleotides and on which there are no apparent surface effects on substrate delivery.

Adenine Nucleotides↗
PubMed1989

Protein kinase C activation alters the sensitivity of agonist-stimulated endothelial-cell prostacyclin production to intracellular Ca2+.

Agonist-stimulated release of prostacyclin (PGI2) from endothelial cells requires elevation of the concentration of intracellular ionized calcium ([Ca2+]i) above a threshold value, and raised [Ca2+]i provides a sufficient transduction signal to account for the extent of PGI2 production. However, chronic activation of protein kinase C has been reported separately to potentiate PGI2 release, but to depress agonist-induced elevations of [Ca2+]i. We show here that pretreatment with phorbol 12-myristate 13-acetate (PMA) dose-dependently induces PGI2 release over many minutes after a significant lag period without any change in [Ca2+]i. In addition, PMA potentiates the transient release of PGI2 in response to agonists in a complex manner depending on the time of pre-incubation and the concentrations of both PMA and agonist. Concomitant measurement of [Ca2+]i and PGI2 release demonstrates that PMA pretreatment dose-dependently inhibits both the peak [Ca2+]i transient and the subsequent steady-state elevation of [Ca2+]i in response to agonists. Determination of the quantitative [Ca2+]i/PGI2 dose/response relationship, when PGI2 release is driven purely by elevating [Ca2+]i with ionomycin, demonstrates that PMA also enhances the Ca2+-sensitivity of PGI2 release. The observed effects of PMA on PGI2 release can be explained quantitatively by its abilities to lower the threshold [Ca2+]i required for PGI2 synthesis and to depress the peak [Ca2+]i evoked by agonist. We propose that these effects are due respectively to actions of PMA on phospholipase A2 and on a G-protein (Gp) that couples activated receptors to phospholipase C.

Calcium↗
PubMed1989

Isolation and sequence analysis of proteins from mouse forebrain using two-dimensional gel electrophoresis coupled to high-pressure liquid extrusion.

This report presents a technique for recovery of mouse forebrain proteins from two-dimensional sodium dodecyl sulfate-polyacrylamide gels for subsequent primary structure determination. Proteins were visualized by Coomassie staining or salt precipitation and manually cut out of the gel. Excised spots were minced and loaded into an empty precolumn of a reversed-phase high-performance liquid chromatography system. Purified protein was extruded from a gel matrix by pressurized liquid, then separated from gel contaminants by reversed-phase gradient elution, and finally collected in siliconized tubes or on polybrene-coated filter disks for gas-phase sequencing. Several mouse and rat forebrain proteins were purified by this method and sequenced. Three previously unidentified mouse brain proteins with molecular weights of 4,000, 12,000, and 18,500 were partially sequenced and three hemoglobin fragments were structurally identified and mapped. Ribonuclease A, myoglobin, adrenocorticotropin, and bovine somatotropin were also subjected to two-dimensional (2-D) analysis and partially sequenced. Recovery values of 27-95% were obtained for extruded 14C-labeled ribonuclease, carbonic anhydrase, and bovine serum albumin out of sodium dodecyl sulfate-polyacrylamide gel electrophoretic gels. Losses resulting from the multiple handling steps of a 2-D gel separation process were also investigated. Recoveries of 12-17%, as determined by sequencing signals, were achieved. These latter recovery values reflect overall losses incurred in gel-focusing, gel-sizing, staining, destaining, high-pressure liquid extrusion, and N-terminal blockage. This work demonstrates that an array of protein spots can be systematically identified or defined by partial sequencing after high-pressure liquid extrusion from a 2-D gel matrix.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylic Resins↗
PubMed1989

Insulin-like effects of histones H3 and H4 on isolated rat adipocytes.

Crude preparations of histones had insulin-like actions in isolated adipocytes. This activity was attributed to the arginine-rich histones, H3 and H4. The metabolic effects of purified H3 and H4 on isolated adipocytes were similar to those of insulin in a number of respects. Like insulin, H3 and H4 stimulated the incorporation of both glucose and pyruvate in isolated cells and stimulated intercellular oxidation of glucose; in contrast, the lipolytic agents ACTH and isoproterenol actually inhibited the incorporation of pyruvate into adipocytes. In contrast to the effects of the lipolytic hormones, the effects of H3 and H4, like insulin, were not blocked by the presence of adenosine deaminase in the medium. The same concentrations of phenylarsine oxide were required to inhibit the stimulation of glucose incorporation whether by insulin or by histones. Furthermore, the addition of H4 or insulin to isolated adipocytes resulted in the increased phosphorylation of 17 kDa phosphoproteins as detected by two-dimensional electrophoresis. The insulin-like effect of the active histones was specific to their structure. Lysine-rich histones (H1, H2A and H2B), various polycations, and proteolytic fragments of purified H3 or H4 were all inactive. It is unknown whether this phenomenon might imply a physiological function for such endogenous molecules; however, a comparison of the detailed effects of insulin and histones might be informative in terms of common intracellular transduction systems.

Adipose Tissue↗
PubMed1989

Endothelial prostacyclin release in systemic lupus erythematosus.

The ability of sera from patients with SLE to stimulate endothelial cell prostacyclin production was studied using a standardized assay system for testing the effects of serum on cultured human endothelial cell monolayers. The effects of 20 normal and 32 SLE sera on endothelial prostacyclin production were measured. No differences between the rates of prostacyclin production were seen between the two groups, either basally or when prostacyclin release was stimulated with thrombin or bradykinin. In the SLE samples there was no correlation between anticardiolipin IgG or IgM titres and their ability to stimulate basal or agonist-induced prostacyclin release. These results suggest that the elevated risk of thrombosis in SLE patients is not associated with inhibition of endothelial cell prostacyclin synthesis.

Adolescent↗
PubMed1989

von Willebrand factor is an acute phase reactant in man.

Plasma von Willebrand factor antigen (vWfAg) concentrations in 19 patients with acute infectious illnesses of bacterial, viral or parasitic origin were significantly elevated with a mean greater than 3-fold above normal. In individual patients the elevation of vWf correlated strongly with the elevation of serum C-reactive protein (CRP). When patients were studied longitudinally, vWfAg and CRP concentrations both returned to normal values over 3-4 weeks. Similarly, in 14 volunteers infected with cold virus, vWfAg and CRP levels rose significantly and fell together during the course of infection. VWf is thus an acute phase reactant in man.

Acute-Phase Proteins↗
PubMed1989

Lysosomal hydrolases of human vascular cells: response to agonists of endothelial function.

Endothelial injury has been proposed as a feature of a wide variety of vascular diseases, and release of endothelial lysosomal hydrolases could contribute to the pathological changes seen. We have determined the relative activities of 14 glycosidases, two esterases and four peptide hydrolases in human umbilical vein endothelial cells and investigated whether known agonists of endothelial function, or materials known to modulate hydrolase secretion in other phagocytic cells, influenced the activity or secretion of these enzymes by human umbilical vein endothelial cells. Hexosaminidase, beta-galactosidase, beta-glucuronidase and alpha-iduronidase accounted for most of the measured glycosidase activity. Acid phosphatase activity greatly exceeded arylsulphatase activity, and most of the measured peptidase activity was due to acid peptidases. Optimum pH and apparent Km values were determined for the most abundant hydrolases. Exposure of human umbilical vein endothelial cells to bradykinin, thrombin or interleukin-1 resulted in negligible release of either hexosaminidase or lactate dehydrogenase (LDH), in contrast to phorbol myristate acetate, which caused a parallel, dose-dependent release of both enzymes. Treatment of these cells with calcium ionophore A23187, trypsin or platelet-activating factor, caused less than 10% release of either hexosaminidase or LDH. Agents known to modulate lysosomal enzyme secretion by other phagocytic cells failed to induce selective secretion of lysosomal enzymes by human umbilical vein endothelial cells.

Bradykinin↗
PubMed1989

Circulatory responses to laryngoscopy: the comparative effects of placebo, fentanyl and esmolol.

The circulatory response to a 30-second laryngoscopy followed by orotracheal intubation was recorded in 60 patients of ASA physical status III or IV undergoing a variety of non-cardiac surgical procedures. Patients were randomly allocated to either the placebo, esmolol (500 micrograms.kg-1.min-1 X 6 minutes, followed by 300 micrograms.kg-1.min-1 X 9 minutes), or fentanyl (0.8 microgram.kg-1.min-1 X 10 minutes) group, and the observer was blinded to the infusion administered. Esmolol blunted the heart rate (HR) response, while fentanyl decreased it below the baseline and maintained it there, in spite of laryngoscopy. Similarly, fentanyl decreased the systolic (SBP), mean (MBP) and diastolic blood pressures (DBP) significantly below the baseline, while these pressures were either retained at or elevated slightly above control in the esmolol group. In these doses, the HR response to laryngoscopy was more effectively blocked by fentanyl, while esmolol better retained perfusion pressure. There were no complications or ischaemic electrocardiographic changes in any patient.

Adrenergic beta-Antagonists↗
PubMed1989

A sensitive fluorometric assay for measuring xanthine dehydrogenase and oxidase in tissues.

The conversion of xanthine dehydrogenase to a free radical producing oxidase is an important component of oxygen-mediated tissue injury. Current assays for these enzymes are of limited sensitivity, making it difficult to analyze activities in organ biopsies or cultured cells. The xanthine oxidase-catalyzed conversion of pterin (2-amino-4-hydroxypteridine) to isoxanthopterin provides the basis for a fluorometric assay which is 100-500 times more sensitive than the traditional spectrophotometric assay of urate formation from xanthine. Enzyme activity as low as 0.1 pmol min-1 ml-1 can be measured with the fluorometric pterin assay. Xanthine oxidase is assayed in the presence of pterin only, while combined xanthine dehydrogenase plus oxidase activity is determined with methylene blue which replaces NAD+ as an electron acceptor. The relative proportions and specific activities of xanthine oxidase and dehydrogenase determined by the fluorometric pterin assay are comparable with the spectrophotometric measurement of activities present in rat liver, intestine, kidney, and plasma. The assay has been successfully applied to brain, human kidney, and cultured mammalian cells, where xanthine dehydrogenase and oxidase activities are too low to detect spectrophotometrically.

Allopurinol↗